Joint Beamforming and Artificial Noise Design in Intelligent Reflecting Surface Aided Secure Wireless Communications

In this paper, we study an intelligent reflecting surface (IRS)-assisted secure wireless communication system, in which a multi-antenna access point (AP) communicates with a single antenna legitimate user in the presence of multiple single-antenna eavesdroppers. In order to effectively prevent eavesdroppers from receiving target information so as to improve the security of the network, artificial noise (AN) is injected into the transmit signal of the AP. For the purpose of power efficiency, we study the problem of minimizing the total power consumption subjected to a target secrecy rate constraint in an IRS-assisted secure communication system. In order to solve this non-convex problem, we decompose the problem into a two-level problem and an iterative problem, which are summarized in our solution by optimizing the two sub-problems successively. Numerical results show that our algorithm can effectively reduce the power consumption and improve the system security performance by optimizing the AP transmitting vectors, AN covariance matrix and IRS reflecting phase.